• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.1 s.92
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• pp.26-32
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• 2005

Open-ended coaxial probe is used to measure complex permittivities of materials in a wide bandwidth. Complex permittivity measured by a conventional coaxial probe suffers from severe fluctuation due to instrumental uncertainty when the difference between reflection coeffcients of reference and measuring materials is small. In this paper, open-ended coaxial probe with protruding inner conductor is suggested to increase the difference between reflection coefficients of reference and measuring materials. Its validity is assured by FDTD simulation and actual measurement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.52-59
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• 2006

To construct its complex permittivity from the reflection coefficient of a thin film such as PCB substrate measured by open-ended coaxial probe, an integral equation is formulated using modal analysis and equivalent source. The accuracy of the conversion model based on the integral equation is confirmed in both cases of converted complex permittivities calculated from numerically computed and actually measured reflection coefficients. And the maximum valid frequency of open-ended coaxial probe is limited by the size of its flange.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.8
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• pp.19-26
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• 1999

umerical simulations are performed to estimate how strongly the manufacturing error of an open-ended coaxial probe affects its measured complex permittivity of a contacted medium. The reflection coefficients of several dielectric materials contacted with an open-ended coaxial probe are calculated by employing the FDTD method. And then those complex permittivities are reconstructed by applying the calculated reflection coefficients into a new imaginary transmission-line model, which reveals more physically meaningful than the conventional model. It is found that the reconstructed complex permittivities suffer from significant error in spite of a slight imperfection of open-ended coaxial probe.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.1 s.92
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• pp.33-39
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• 2005

Complex permittivities of material in a wide bandwidth are measured by using an open-ended coaxial probe. To obtain a confident complex permittivity profile, the accuracy of measured reflection coefficients and the stability of the conversion model should be guaranteed in advance. In this paper, the sensitivity of our conversion model is analyzed by employing two instruments with different uncertainties. And various factors effected on the accuracy of measured reflection coefficients are investigated in experiment.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.10
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• pp.7-12
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• 1998

The wave reflections from several types of open-ended coaxial probes contacted on the various materials have been analyzed precisely by using the finite-difference time-domain(FDTD) technique in this paper. Due to the coordinate transformation from three-dimension to two-dimension, the computation was performed very efficiently. It was found that the reflection from an open-ended coaxial probe reduces as frequency or diameter of a coaxial line increases. The reflections from multi-layered media were also analyzed by the FDTD method. This analysis technique was verified by comparison with measurements and theoretical computations.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.115-123
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• 2000

Characterizing the electromagnetic properties of concrete is essential to the enhancement of accuracy and reliability in nondestructive testing of concrete structures using electromagnetic techniques. To establish a data base for the properties of concrete, a measurement technique has been developed and a set of data has been obtained for the frequency range of 1~6 GHz. As moisture content is one of major contributing factors to determine permittivity of dielectric material, moisture content is varied during the measurement. An application of a measurement system which consists of open-ended coaxial probe and automatic network analyzer to concrete and mortar specimens is studied. For this, calibration techniques, size of specimens, and number of measurements necessary to obtain reliable data are investigated. From the measured data, it is shown that moisture content plays an important role to determine the permittivity of specimens. As the moisture content increases. The permittivity of specimens show tendency to approach the permittivity of water.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.470-474
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• 1996

The dielectric properties, dielectric constant (${\varepsilon}‘$) and loss factor (${\varepsilon}’$), of skin and pulp of fresh ginseng were measured from $25^{\circ}C$ to $67^{\circ}C$ using an open-ended coaxial probe technique for 915 MHz and 2450 MHz. Pulp and skin had dielectric constant of $30{\sim}64$ and loss factor between 10 and 20, each variable having a respective frequency dependence typical of materials with high water content. Although the loss factor was nearly constant, the dielectric constant increased as moisture content increased. The dielectric constant of ginseng pulp increased as temperature increased (temperature ${\leq}56^{\circ}C$), but any significant differences were not found in skin dielectric properties. Penetration depth for fresh ginseng were about 2 cm at 91.5 MHz and 1cm at 2450 MHz.

• Journal of electromagnetic engineering and science
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• v.12 no.2
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• pp.161-165
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• 2012

The electrical properties of pig internal organs including lung, liver, heart, kidney, blood, stomach, and small intestine are measured using an open-ended coaxial probe and an improved virtual transmission-line model. The measured complex permittivities of the pig organs are compared with the given values of the corresponding human organs. A similarity between these values is confirmed. For organs such as lung, liver, heart, and kidney that have regular texture and contents, the complex permittivities are almost identical to those of the corresponding human organs. The complex permittivities of human and pig blood are also very close in value. However, relatively large deviations are observed for the cases of stomach and small intestine because the internal contents of these organs significantly affect the measured electrical properties.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.7
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• pp.22-27
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• 2001

In this paper, the complex permittivity of various dielectrics such as powder(sugar and flour) and solid(teflon and acrvl) are measured by using an open ended coaxial-line probe, which is self designed and manufactured, The probe is connected to a vector network analyzer(VNA) through a coaxial cable, The end of the cable is corrected by using an OSL(open, short, and load) calibration kit, The phase difference, which is produced by inserting the probe at the end of the line. is compensated by using the numerically calculated reflection coefficient of distilled water, The complex permittivity is reconstructed by inserting the measured reflection coefficient, which is produced at the interface between the probe and measuring material, into ,an virtual conical cable conversion model. Over a wide frequency range from 30 MHz to 3 GHz, the measured complex permittivitis of various powder and solid using the our method are compared with the results, which are measured by using an transmission-line method of the Korea Research Institute of Standards and Science(KRISS).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.5
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• pp.17-24
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• 2000

Complex permittivity of dry sand is measured by using an open-ended coaxial probe, which was self-designed and manufactured. As a simple calibration scheme of the probe, the phase difference between the measured and the calculated reflection coefficients of pure water is subtracted from the phase of the measured reflection coefficient for dry sand. And then the complex permittivity of dry sand is reconstructed by applying its measured reflection coefficient into an improved imaginary transmission-line model. The accuracy of our measurement scheme is verified by showing that its reconstructed complex permittivity approaches the precise value of dry sand.